Ticks pierce the skin of animals causing infection and are known to spread disease. Protecting livestock from ticks is a major concern of the agriculture industry. Ticks are also known to spread human diseases including Lyme disease.
Over the years, many methods have been developed for controlling tick populations. One common practice used in many countries, including developing countries, is to spray the entire animal with a pesticide. Such spraying operations can pose environmental hazards for the surrounding area as well as health hazards for individuals working near the spraying facility. Using decoys in combination with a pesticide is an attractive alternative to spraying the entire animal. Less pesticide is required since the ticks will be attracted by the decoy to the site where the pesticide is located. Many chemical and visual lures have been used in the past with varying degrees of success. For example, U.S. Pat. No. 4,493,161 and U.S. Pat. No. 229,222 show the uses of visual lures shaped like an animal or plant, respectively. Pheromone attractants have also been used in combination with pesticides. For example, U.S. Pat. No. 4,888,361 to Sonenshine et al. discloses a plastic decoy shaped like a female tick which is impregnated with a sex attraction pheromone, mounting pheromone and a pesticide. In Sonenshine et al., the sex attraction pheromone and mounting pheromone were selected to take advantage of feeding and mating characteristics of many ticks wherein a fed male tick will detach from a host in response to an attraction pheromone and attempt to copulate with a female tick in response to a mounting pheromone.
A problem with using decoys is that they must be specific for the pest to be destroyed. If the ticks to be destroyed do not respond to the decoy which is used, the protection scheme will be ineffective.
Little has been documented of pheromonal regulation of behavior in Ixodes scapularis and other Ixodes spp. Pheromones generally affect mate-finding and off-host assembly of ticks. Assembly pheromones induce formation of off-host clusters of various stages and sexes of ticks through arrestment of movement upon contact. Ticks are generally classified as hard ticks or soft ticks, with significant differences between the groups in biology and behavior (such as duration and frequency of feeding and host species). Tick assembly behavior is well characterized from soft ticks (14 species) and attraction occurs in response to aqueous/saline extracts of tick exudate (excreta, feces). Compounds that have been identified from these extracts and eliciting assembly in Argas (soft ticks) include purines or purine-like compounds such as guanine, uric acid, xanthine, and adenine. Behavioral evidence of a water-soluble pheromone inducing assembly has been reported Experientia 33:680-682), Ixodespersulcatus (Uspensky, L. V. and O. Y. Emelyanova [1980] "On the existence of pheromone relations in ticks of the genus Ixodes" Zool. Zh. 59:699-704) and I. ricimus (Hajkova, C. and M. G. Leahy [1982] "Pheromone-regulated aggregation and larvae, nymphs, and adults of Ixodes ricinus L. (Acarina: Ixodidae)" Folia Parasitol. 29:61-67).
Currently there are no pheromone-based methods of control or surveillance (monitoring) for Ixodes ticks. Methods of control against Ixodes ticks (the vectors of Lyme disease, human ehlichiosis and human babesiosis) include use of acaricides (granules and sprays) to reduce tick abundance on lawns and woodland edges, reduction of deer as hosts of ticks, treatment of mice (as tick hosts) with permethrin cyfluthrin, delamethrin, bifentrhin and reduction of tick habitats (vegetation, leaf litter) around houses. Reduction of disease transmission is also obtained through use of repellents on skin and clothing, and timely removal of attached ticks. Acaricides are the primary method used for tick control and those registered for such use include carbaryl, chlorpyrifos, diazinon, cyfluthrin, s-fenvalerate, fluvalinate and permethrin. Repeated and widespread use of these compounds elicits considerable environmental concern (run-off, non-target effects) and cost for area-wide applications.
The combination of acaricide with pheromones has the advantages of enhancing acaricide efficacy by attracting ticks to the acaricide, acting as a species-targeted control method, and the potential for reducing environmental contamination by treating only high risk areas (i.e., backyards, parks, etc.). The concept of combining pheromones with acaricides for tick control has been tested in several successful field trials using extracts of fed males of several species of Amblyonma that produce an aggregation-attachment pheromone (Norval, R. A. I., C. E. Yunker, I. M. Duncan and T. Peter [1991] "Pheromone/acaricidemixtures in the control of the tick Amblyomma hebraeum: Effects of acaricides on attraction and attachment" Exp. and Appl. Acarol. 11:233-240). With the subsequent identification of pheromone components, a synthetic pheromone mixture for Amblyomma hebraeum and A. variegatum (Norval, R. A. I., D. E. Sonenshine, S. A. Allan, M. J. Burridge [1996] "Efficacy of pheromone-acaricide-impregnated tail-tag decoys for controlling the bont tick, Amblyomma hebraeum (Acari: Ixodidae), on cattle in Zimbabwe" Exp. Appl. Acarol. 20:31-46) was developed and incorporated, along with acaricide, into a slow-release plastic tag for tick control on cattle. Field trials for control of A. hebraeum on cattle in Zimbabwe (Norval el al. [1996] supra) and A. variegatum on cattle in Guadeloupe (Allan, S. A., N. Barre, D. E. Sonenshine, and M. J. Burridge [1998] "Efficacy of tags impregnated with pheromone and acaricide for control of Amblyomma variegalum" Med. Vet. Entomol. 12:141-150) resulted in high levels of tick control for three months. A patent by Norval et al., 1994 (Attractant decoy for controlling bont tick, U.S. Pat. No. 5,296,227) describes the use of tick pheromone components in conjunction with acaricides, however, these pheromone components do not elicit attraction of Ixodes scapularis. The use of the tick pheromone, 2-6-dichlorophenol, considerably enhanced mortality of the American dog tick (Dermacentor variabilis) in a study by Sonenshine et al. (Sonenshine, D. D., D. Taylor, and G. Corrigan [1985] "Studies to evaluate the effectiveness of sex pheromone impregnated formulations for control of populations of the American dog tick, Dermacentor variabilis (Say) (Acari: Ixodidae)" Exp. Appl . Acarol. 1:23-24), however, this pheromone is not attractive to Ixodes ticks.